let _Vue = null;

export default class VueRouter {
  static install(Vue) {
    // 1、判断当前插件是否已经安装
    if (VueRouter.install.installed) {
      return;
    }
    VueRouter.install.installed = true;
    // 2、把 vue 构造函数记录到全局变量
    _Vue = Vue;
    // 3、把创建 vue 实例时候传入的 router 对象注入到 vue 实例上
    // 混入
    _Vue.mixin({
      beforeCreate() {
        if (this.$options.router) {
          _Vue.prototype.$router = this.$options.router;
          this.$options.router.init();
        }
      }
    });
  }
  constructor(options) {
    this.options = options;
    this.routeMap = {};
    this.data = _Vue.observable({
      current: '/'
    });
  }
  init() {
    this.createRouteMap();
    this.initComponents(_Vue);
    this.initEvent();
  }
  createRouteMap() {
    // 遍历所有的路由规则，把路由规则解析成键值对的形式，存储到 routeMap 中
    this.options.routes.forEach(route => {
      this.routeMap[route.path] = route.component;
    });
  }
  initComponents(Vue) {
    const self = this;
    Vue.component(
      'router-link', {
        props: {
          to: String
        },
        render(h) {
          return h('a', {
            attrs: {
              href: '#' + this.to
            },
            on: {
              click: this.clickHandler
            }
          }, [this.$slots.default]);
        },
        methods: {
          clickHandler(e) {
            window.location.hash = '#' + this.to;
            this.$router.data.current = this.to;
            e.preventDefault();
          }
        }
      }
    );
    Vue.component('router-view', {
      render(h) {
        const conmponent = self.routeMap[self.data.current];
        return h(conmponent);
      }
    });
  }
  initEvent() {
    window.addEventListener('load', this.hashChange.bind(this));
    window.addEventListener('hashchange', this.hashChange.bind(this));
  }
  hashChange() {
    if (!window.location.hash) {
      window.location.hash = '#/';
    }
    this.data.current = window.location.hash.substr(1);
  }
}